Julia Galef: Think Rationally via Bayes' Rule | Big Think

Think Rationally via Bayes' Rule
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Bayes’ Rule is a formalization of how to change your mind when you learn new information about the world or have new experiences.
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JULIA GALEF:

Julia Galef is a New York-based writer and public speaker specializing in science, rationality, and design. She serves on the board of directors of the New York City Skeptics, co-hosts their official podcast, Rationally Speaking, and co-writes the blog Rationally Speaking along with philosopher of science Massimo Pigliucci. She has moderated panel discussions at The Amazing Meeting and the Northeast Conference on Science and Skepticism, and gives frequent public lectures to organizations including the Center for Inquiry and the Secular Student Alliance. Julia received her B.A. in statistics from Columbia in 2005.
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TRANSCRIPT:

I’d like to introduce you to a particularly powerful paradigm for thinking called Bayes’ Rule. Back in the Second World War the then governor of California, Earl Warren, believed that Japanese Americans constituted a grave threat to our national security. And as he was testifying as much to Congress, someone brought up the fact that, you know, we haven’t seen any signs of subterfuge from the Japanese American community. And Warren responded that, “Ah, this makes me even more suspicious. This is an even more ominous sign because that indicates that they’re probably planning some major secret timed to attack á la Pearl Harbor. And this convinces me even more that the Japanese Americans are a threat.”

So this pattern of reasoning is what sustains most conspiracy theories. You see signs of a cover up – well, that just proves that I was right all along about the cover up. You don’t see signs of a cover up, well that just proves that the cover up runs even deeper than we previously suspected.

Bayes’ Rule is provably the best way to think about evidence. In other words, Bayes’ Rule is a formalization of how to change your mind when you learn new information about the world or have new experiences. And I don’t think that the math behind – the math of Bayes’ Rule is crucial to getting benefit out of it in your own reasoning or decision making. In fact, there are plenty of people who use Bayes’ Rule on a daily basis in their jobs – statisticians and scientists for example. But then when they leave the lab and go home, they think like non-Bayesians just like the rest of us.

So what’s really important is internalizing the intuitions behind Bayes’ Rule and some of the general reasoning principles that fall out of the math. And being able to use those principles in your own reasoning.

After you’ve been steeped in Bayes’ Rule for a little while, it starts to produce some fundamental changes to your thinking. For example, you become much more aware that your beliefs are grayscale, they’re not black and white. That you have levels of confidence in your beliefs about how the world works that are less than one hundred percent but greater than zero percent. And even more importantly, as you go through the world and encounter new ideas and new evidence, that level of confidence fluctuates as you encounter evidence for and against your beliefs.

Also I think that many people, certainly including myself, have this default way of approaching the world in which we have our preexisting beliefs and we go through the world and we pretty much stick to our beliefs unless we encounter evidence that’s so overwhelmingly inconsistent with our beliefs about the world that it forces us to change our minds and, you know, adopt a new theory of how the world works. And sometimes even then we don’t do it.

So the implicit question that I’m asking myself that people ask themselves as they go through the world is when I see new evidence, can this be explained with my theory. And if yes, then we stop there. But, after you’ve got some familiarity with Bayes’ Rule what you start doing is instead of stopping after asking yourself can this evidence be explained with my own pet theory, you also ask well, would it be explained better with some other theory or maybe just as well with some other theory. Is this actually evidence for my theory.

Produced/Directed by Jonathan Fowler and Dillon Fitton

[sinisterkritik]

It's actually surprising how many people claim to be "open minded" but then quickly retreat back to their comfort zones once presented with a radical new perspective.

[drstrangelove]

Better yet, actively try to poke holes in the things that you believe the most.

[TheRealMake-Make]

Bayes' Theorem is an important tool in probability, but my statistics book was terrible in its attempt to verbalize it.  Basically, it is very much as Julia described it: we think we know (with some degree of certainty) how an event will occur.  However, we often learn in the future that our belief was wrong, so we go back and revise our beliefs (posterior probabilities).  My book gives a very boring example having to do with credit cards and the probability that someone will default, so I won't bore anyone with those details.  The implications are important, though: if something more accurate comes along than what we believe to be right and correct, we must be willing to change our paradigm in order to have a better understanding of the way the world works.  

[psyience]

You neglected to explain Bayes' rule.

[GabrielKnightz]

"Is there any knowledge in the world which is so certain that no reasonable man could doubt it?"
-Bertrand Russell.

[kieranreilly]

hey are you gonna tell us what Bayes' rule is or do we have to pay for that?

[NiteSaiya]

Realizing most people didn't already think like this is what ended my rebellious teen phase. Learning that my parents had gifted me something from infancy most people require years of schooling to obtain.

[Titan]

Well, part of the problem is that to go into Bayes requires more time than is alloted to this Big Think introduction video. As far as I can extrapolate, Julia only had time to talk about the benefits of using Bayes Theorem, not necessarily what it is or how to use it in everyday thinking.

But about those equations: (A|B) is the probability that B is true given that A is true. That's what the symbol "|" means. I've found this out very recently.

Relevance: ....hard to talk about in 500 chars

[dry]

Thanks. My first Introduction to clear thinking was SI Hayakawa’s Language in Thought and Action years ago. Got me started thinking about thinking.

[lllCockroachlll]

She states some of the principles of Korzybski's General Semantics. Look up the book "Language in thought and action" by Hayakawa, or "Language habits in human affairs" by Irving J. Lee

[bat-amgalanbat-erdene]

It's a very good informative video. I'm amazed by how much dislike it got. Maybe the prerequisites to understand this video is beyond those who have disliked.

[asrarul]

THANKS a lot for explaining the Bayes Rule in story with no equations. Very powerful. Love from Bangladesh

[odiemonster]

Love this: the use of mathematical principles outside mathematics :) awesome

[willcravens]

you didn't actually introduce Bayes' Rule

[OldKingSol]

I was expecting some actual definition of Bayes' Rule, and was mildly disappointed that no real explanation of the rule, itself, was given. However, I think part of the point of videos like these is to let people know what's out there, so they can decide what aspects of thought they're interested in, so they can go out and learn more on their own. There's lots about Bayes' theory on Google. I never would have known that if not for this video piquing my interest. So thanks! :-)

[Endrance]

for those of you who don't know what baye's rule is, it's quite simple: a change in your principles because something in the world contradicts your principles. living by bayes rule means you would use this logic to your benefit. she did explain what it was in the video, however, i admit, she didn't bother stating what it was by prefacing it with "baye's rule is"

[andrewcrawford]

Ah. So that's the name of that method of thinking.

Love it. Great video.

[tjwhalan]

There is an easier way to say this: Don't hold a stake in the way you think the world works. That way when evidence comes along that is better then what you previously believed you give the new evidence the thought it deserves.

[Rayquesto]

I knew before looking at the comments someone would say that and I agree, but once you look it up, I bet this video is 10times more helpful than before.

[coreycox]

I have seen this before. This makes more sense to me now, as I have recently had an experience discussed.